The invention relates to an improved drip irrigation pipe for effecting drip irrigation above the ground.
Many means for effecting a trickle outlet from irrigation pipes are known. These means may include elongated dripper units inserted in an irrigation pipe, elongated branch pipes of very narrow diameter leading off a main supply pipe, button-like dripper units inserted in a supply pipe and having a labyrinth path for the water between said supply pipe and the outlet from the unit, and other systems.
The main problems of drip irrigation are concerned with flow pressures and size of apertures, i.e. the pressures must be great enough to permit constant drip flow over the entire length of a long pipe without undue head loss, but not too great to cause damage to the pipe or to the outlets. The outlets must be large enough to prevent clogging by impurities, but must not be too large to cause a jet outflow to be formed.
In U.S. Pat. No. 3,727,841 (Hengesbach) pipes with outlets are described and claimed, which outlets cause jet sprays for the irrigation of plants. In one embodiment pairs of outlets in the wall of the pipes are arranged at such angles relative to each other that the jet emerging from one outlet of the pair impinges on that from the other outlet, so that a fog or mist covering a larger surface than that covered by a straight jet is created.
In U.S. Pat. No. 3,512,363 (Whear) a liquid distribution tube is described and claimed having cylindrical i.e. straight-walled discharge bores directed contrary to the axial direction at an angle of 6.degree. to 14.degree. from the axis of the tube. The liquid flowing in the tube is either under high pressure for atomized discharge or without pressure in a tube for subterranean irrigation.